Hitherto, many techniques have been proposed to impart moisture absorbency to, for instance, polyester synthetic fiber or textile goods made therefrom.
For instance, there is a method (1) of treating synthetic fiber with a treating liquid containing an acrylic or polyurethane emulsion and finely powdered natural organic substances such as collagen.
However, according to the above method (1), since the natural organic substance fine powder is merely physically adhered to the synthetic fiber through an emulsion as a binder, the fine powder is likely to be removed by washing, resulting in an inferior durability. An increase of the emulsion ratio to improve the durability hardens the feel of the synthetic fiber, thus making it less applicable to practical use.
There is another method (2) of treating synthetic fibers with a treating liquid containing a modifying agent (monomer), such as polyethylene glycol compounds, for improving moisture absorbency.
The method (2) is superior in durability because the modifying agent forms a hydrophilic layer inside and on the synthetic fiber. However, only a small improvement in moisture absorbency can be observed.
Still another method (3) has been proposed to treat the synthetic fiber with a treating liquid containing a protein aqueous solution and the above modifying agent. The protein solution is obtained by dissolving, for instance, silk fiber in a calcium chloride solution and dialyzing the solution with a cellophane tube.
The method (3) gives at least an improvement in moisture absorbency due to adherence of the protein onto the synthetic fiber but the increase in the protein amount to ensure sufficient moisture absorbency gives a hard feel. On the other hand, an attempt to maintain the soft feel restricts the protein amount, which makes it impossible to obtain sufficient moisture absorbency.
In addition to the moisture absorbency and the feel described above, improvements in hydrophilic nature, antistatic property, and durability are also required for fibers and textiles.